Rooftop temp/perm panel mounting ideas--no penetrations?

[lectraplayer]

I'm experimenting with a 100 watt Harbor Freight kit to see what I can get out of solar, and have been wondering what the best way to secure the panels to the roof without penetrating would be. My first thought is to elevate them slightly with 2x4's for airflow and "just throw 'em down" on the roof of my house, though I'm wondering how easily they'd blow around. Also thought about bricking them down on a sled. What have you found works best?

[Mike90250]

Toss the panel, and keep the useful cardboard box it came in.

Seriously. If the panel will stay on the roof by itself until the wind comes up, and you are just testing, I'd not get too elaborate with trying to mount a nearly worthless panel. I sure would not put one hole in a good roof for the panel.
Use a cable, hang from a vent pipe like a picture ?

[Ampster]

I agree with@Mike90250, it is no worth putting a hole in your roof for such little power. Years ago I had panel like that and .and used a chain to hold it down on a Spanish tile roof. I wired the holes in the back of the frame to the chain and put it on my roof. Anything with enough weigh to keep it from moving when the wind blows should work. .

[lectraplayer]

Putting a hole in my roof is something I'm DEFINITELY trying to stay away from, and my goal is to get an idea how much power per square meter of panel I can expect and how to optimize it. Thanks for the general advice just the same. That's what I was thinking, but wanted to be sure before finding out too late what I should have done.

[Ampster]

Putting a hole in my roof is something I'm DEFINITELY trying to stay away from, and my goal is to get an idea how much power per square meter of panel I can expect and how to optimize it. Thanks for the general advice just the same. That's what I was thinking, but wanted to be sure before finding out too late what I should have done.

Now that I understand your goal more precisely try going to PVWatts to get an opinion in addition to your experiment. https://pvwatts.nrel.gov/
That way you will get a years worth of estimates without having to wait that long. The differences between winter and summer can be quite a lot depending on where you live.

[lectraplayer]

Now that I understand your goal more precisely try going to PVWatts to get an opinion in addition to your experiment. https://pvwatts.nrel.gov/
That way you will get a years worth of estimates without having to wait that long. The differences between winter and summer can be quite a lot depending on where you live.

I remember looking at that, but does it account for certain variables like... maybe... trees? (I have a forest and don't wanna cut 'em down. Also, numbers are nice, but I'm all the time finding that theory can stray quite a bit from actual hardware.

[sdold]

I remember looking at that, but does it account for certain variables like... maybe... trees?

Tree shaded panels produce very little power, best to move them where they will see full sun around midday for as long as possible.

[Ampster]

No it doesn't account for trees.
Numbers are numbers no matter how you get them. Some take more time to collect than others. If you have the time you may have more confidence in your own numbers.. You will still have variation from weather.
I did once see a solar installer with a fancy camera come up with an estimate of shading on two roof locations in a forested site. Try searching on the Internet. Keywords might be solar insolation.
Finally, if Google Project Sunroof is available in your location, it may give you a rough clue about shading.

https://www.google.com/get/sunroof

No numbers involved just shades of yellow and orange.

[lectraplayer]

Tree shaded panels produce very little power, best to move them where they will see full sun around midday for as long as possible.

Not an option I have, given I have trees everywhere. Best I can do is to take samples from educated guesses, and "figure out my equipment" to figure out how to best manage a system in my location.

...though Ampster that's new to me. I may need to check that one out.

[littleharbor]

[QUOTE=lectraplayer;n400050 my goal is to get an idea how much power per square meter of panel I can expect and how to optimize it. .[/QUOTE]



Bear in mind that the Harbor Freight panels are thin film technology and are only half as efficient, (or worse), than crystalline cell technology panels.

[lectraplayer]

Bear in mind that the Harbor Freight panels are thin film technology and are only half as efficient, (or worse), than crystalline cell technology panels.

They must've lied to me then as the box said crystaline cell. The panels are also bricks.

Still not expecting the performance of a high dollar system though.

[MichaelK!]

Years ago I started out with two Harbor Freight kits, for which I replaced almost immediately with better panels after I realized how worthless they were. I made the most rinky-dink frames for them that you could imagine, out of galvanized sheet-rock edging.

https://www.homedepot.com/p/ClarkDietrich-1-1-4-in-x-8-ft-Quicksilver-Metal-Corner-Bead-741339/203171469

They are the strips of light-gauge steel that you place on the edges of your walls to give the plaster a nice straight edge for aesthetics. I welded them together in a truss-like pattern that looks like the structure of an overhead highway sign. Lots of diagonals spaced less than 12" apart. They are still up on the porch roof 6 years later, even though they've been totally out of service now for 3 years. I just don't think they are valuable enough to go up on the roof to retreive them, so I just left them there, sitting, doing nothing.

The point is that the frames I built for them performed admirably well, with the panels surviving 6 years of storms that have toppled 18" oaks. If you made something like them, you could position them on your roof and lash them down with cargo hooks designed for strapping down loads in the back of your pickup truck. If long enough, the strap hooks could be draped over the edge of the roof to some anchoring points down below. The lashing would last till the UV light degrades the plastic to the breaking point, but I'd expect them to give several months of service before needing to be replaced.